(DOCSP-21819): Use 'major' release instead of 'lts' (#922)

* (DOCSP-21819): Use 'major' instead of 'lts'

* add toc

Author: jeff-allen-mongo

source/reference/versioning.txt

@@ -4,7 +4,13 @@
 MongoDB Versioning
 ==================
 
-.. |lts| replace:: Long-Term Support
+.. |lts| replace:: Major
+
+.. contents:: On this page
+   :local:
+   :backlinks: none
+   :depth: 1
+   :class: singlecol
 
 .. important::